lyo SCIENCE AND IMMORTALITY 



And there is nothing inherently improbable in 

 this. Living molecules can certainly feed on in- 

 organic salts, and by inorganic salts can be 

 repaired ; and the same worsted that can darn a 

 stocking can make one. 



It is usually assumed that the first life must 

 have been vegetable life, because only plants can 

 assimilate nitrogen and carbon in inorganic form ; 

 but plants can assimilate only after they are made, 

 and by virtue of their make^ so that the difficulty 

 of the first formation of living matter is not 

 diminished by calling it vegetable. The first 

 combination of nitrogen, oxygen, carbon, and 

 hydrogen, able to build itself up again as it broke 

 down, was probably able to obtain its carbon with- 

 out the aid of that very complex substance called 

 chlorophyll. It is probable, too, that first molecules 

 were not grouped in the structural complexity 

 now seen in cells, but in much simpler formation. 



That, then, is the second theory, which may be 

 held, of course, in conjunction with the third. 



The third and last theory, that life was brought 

 to the world from another planet — from " the 

 moss-grown ruins of another world " — suggested 

 by Sales, Guyon de Montlivault, H. E. Richter, and 

 Ferdinand Cohn, was propounded in particular by 

 two great men. Lord Kelvin and von Helmholtz. 

 The theory suggested that meteors had been the 



